In field emitters using nano materials, carbon nanotubes or carbon nanowires are in the spotlight as electron emitting materials. A carbon nanotube is a structure where a one-dimensional honeycombed plate is wound in a shape of a tube, and shows excellent electrical, mechanical, chemical, and thermal characteristics in applications of various fields. A carbon nanotube having a high aspect ratio can easily emit electrons even in an electric field having a low potential due to its excellent geometric characteristics.
Thus, in recent years, electric field displays and lamps using carbon nanotubes are being widely studied in Korea, and studies on emission of electrons in an infinitesimal area such as a tip of X-ray source devices, atomic force microscopes (AFMs), and scanning electron microscopes (SEMS) are also being activly conducted. A structure where an emitter is formed on a tip type cathode electrode is advantageous in producing carbon natotube (CNT) electron beams having high efficiency and high density such as subminiature devices or micro focusing devices. The emitter on the tip type cathode electrode emits electrons in an infinitesimal area and electric fields are concentrated due to its geometric structure.
FIG. 1 is a view illustrating a field emitter according to the related art.
Referring to FIG. 1, the field emitter according to the related art has a triode structure where an emitter 120 is formed on a tip type cathode electrode 110 and a gate electrode 130 for drawing electrons from the emitter 120 is disposed above the emitter 120.
As illustrated in FIG. 1A, in the triode type field emitter, the gate electrode 130 has a mesh in a form of a net, or as illustrated in FIG. 1B, has a single hole 132 through which electron beams emitted from the emitter 120 can pass.
However, the gate electrode 130 having a mesh can be variously selected according to a thickness of a mesh wire or an opening ratio of the mesh, but cannot prevent leakage of current occurring when electrons emitted from the emitter 120 escape along the mesh. Then, if the leakage current of the gate electrode 130 is high, heat is generated and a possibility of generating an arc between the cathode electrode 110 and the gate electrode 130 increases, reducing stability during electric field emission.
The gate electrode 130 having the hole 132 can reduce leakage currents as a size of the hole 132 increases, but a voltage applied to the gate electrode 130 increases as the size of the hole 132 increases.